Quality control, or QC for short, is an important part of every production process. In QC, the product is checked against specifications, and a decision to continue is made accordingly. Quality control of surfaces is an essential part of processes like cleaning, coating and printingto determine if the applied process has been successful.

The wettability of a surface is a good indicator of the surface properties. The wettability of the surface is evaluated using contact angle measurements. The contact angle of the surface can be used in the QC of multiple processing steps:

  • Prior to treatment, to ensure surface cleanliness
  • After surface treatment, to ensure the desired treatment level and/or coating homogeneity
  • To solve adhesion and wettability related quality control issues

Contact angle measurements can be automated and require only a small measurement area. Contact angles offer a possibility to execute a fast analysis, as large batches can also easily be measured. Contact angles are particularly suitable for surface quality control purposes

  • One of the most surface sensitive techniques
  • Simple, quick and easy to use
  • Independent of the user, especially with automation
  • Gives a quantitative number
  • Well-established, scientific quality control method

The water contact angle measurement alone gives a good estimation of the surface chemistry, but making the measurement with dispersive liquid as well allows you to determine the surface free energy of the surface. The integration of a disposable tip dispenser enables rapid surface free energy measurements. Surface free energy is the only method available that can separate the dispersive and polar components of the surface energy. Contact angle measurements can also be used to check the homogeneity of the coating, which is impractical, if not impossible, with often used dyne pens and inks.

Apart from surface chemistry, roughness also plays a role in wettability. Many processes such as plasma or flame treatments affect not only the chemistry of the substrate but may also change the roughness. By combining a topography measurement with the contact angle, it is possible to separate the effect of roughness from contact angle.

A fully automated Theta contact angle meter excludes any user interference and thus enhances your result repeatability. OneAttension software includes a special quality control mode for simplifying the QC procedure. OneAttension also offers unique quality control features such as a the creation of a limited operating environment for operators, making the operation as simple and quick as possible, with time-saving batch analyses and result report tailoring for your needs.


Plasma and corona treated surfaces

Plasma and corona treatments are used for the cleaning and activation of surfaces before further processing steps such as printing, bonding, painting, varnishing or coating. They are used for solving issues relating to adhesion and wettability in many industries. 

Industrial coatings on paper and board for packaging and printing

For packaging, board surfaces are often extrusion-coated for resistance against moisture and aging. To optimize the printing quality, the surfaces are also commonly plasma or corona treated to increase the wettability between the ink and the surface. Contact angle QC is a simple method to ensure the functionality of the coatings and treatments.

Industrial coatings for medical device manufacturing

Different kinds of industrial coatings are applied to medical devices to increase their functionality, for example in selective fluid flow. The coatings are used in multiple applications including diagnostics, biomedical and pharmaceutical. 

Biomedical implant surface treatments

The biocompatibility of a biomedical implant can be affected by modifying the wettability of the implant surface. Both increasing surface roughness and altering surface chemistry influence the wettability and can be characterized to ensure implant quality.

Cleanliness of glass and touchscreens

The cleanliness of a glass surface has a direct effect on the quality of any subsequent processing steps such as inkjet printing of bottles or using adhesives for label application. Measuring glass contamination helps in reducing waste and ensuring efficient production.

Industrial coatings for solar panels

Solar panels are often coated with photovoltaic and anti-reflective coatings to ensure optimal efficiency. Cleanliness affects the efficiency of the panel and influences the adhesion between different coated layers. The contact angle can be utilized in the quality control of the panels in manufacturing. 

Quality control of transformer oils

Insulating oils are used around the coils in power transformers to provide cooling, insulation and protection against corona and arcing. Transformer oils are exposed to mechanical and electrical stress, as well as to chemical contaminations, during the operation of the transformer. Over time the functionality of the oil is reduced, and this can lead to transformer failure and power outages. Regular testing of the oil can ensure quality and prevent costly downtime.

There are two standards created for monitoring the contamination level of transformer oils by interfacial tension measurement; IEC 62961 and ASTM D971. In both standards, the interfacial tension is measured using the Du Noüy ring method. Oil and water interfacial tension correlates with the purity and functionality of the oil. A decrease in interfacial tension in the transformer oil occurs due to the accumulation of contaminants or due to the formation of oxidation by-products. The Sigma 702ET operates fully automatically and guides the user through the measurement using either standards.

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